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IS Barrier Use
Are IS Barriers Required for Instrumentation Rated Class II?


I want to know how much is necessary to use IS Barrier for Instrumentation Rated Class II (Hazardous because combustible or conductive dusts are present)?

Best Regards
Hamid Ankouti

Please read Article 504 of the National Electrical Code then return here with more specific questions.

Here's a link to a Hubbell-Killark article which includes a reprint from the 2011 edition:

>Here's a link to a Hubbell-Killark article which includes a
>reprint from the 2011 edition:

Dear my friend
thanks for your reply, i read this article, but just wrote Apparatus in which the circuits are not necessarily intrinsically safe themselves but that affect the energy in the intrinsically safe circuits and are relied on to maintain intrinsic safety. Associated apparatus may be either of the following:

(1) Electrical apparatus that has an alternative-type protection for use in the appropriate hazardous (classified) location

(2) Electrical apparatus not so protected that shall not be used within a hazardous (classified) location

and didn't noted which zone.

i have some analog card in steel making plant, i want to know are they necessary to use intrinsically safe barrier for them?

Best regards
Hamid Ankouti

Other than simple apparatus, the equipment must be rated intrinsically safe. The equipment documentation must contain a control drawing, and the equipment must be installed as depicted.

>Other than simple apparatus, the equipment must be rated
>intrinsically safe. The equipment documentation must
>contain a control drawing, and the equipment must be
>installed as depicted.

in the below link, this pdf in page 7 write the intrinsic safety is the only safe technique suitable for zone 0 and is often the preferred approach for zone 1 (division 1).

thanks for your reply. i wanted to know that is Intrinsically Safety Barrier is necessary for Steel making plant or No. if yes, how much is necessary.

All the best
Hamid Ankouti

You did not quote the referenced statement in its entirety and thus eliminated some of the context. In the article it is preceded with "For all practical purposes".

That takes us back to my answer to your thread title question. Quite simply, an intrinsically safe system is not required in any hazardous location. At least not that I'm aware of in U.S. hazardous locations (NEC/NEMA/UL/NFPA).

Not familiar with IEC requirements, but I believe the NEC has included Zones in Articles 505 and 506 to provide at least a small measure of global standardization. As far as I can tell, Zone 0 and Zone 1 are Class I locations and the context of your query is a Class II hazardous location.

In a typical IS system, the non-HL/IS-rated equipment is placed in an unclassified location. Only equipment that must be in the HL is located there (such as the simple apparatus of the IS circuit). The interconnecting wiring is run through an IS Barrier located on the unclassified side of the HL boundary. Any NEC Chapter 3 wiring method is permitted for the IS circuit within the HL, subject to protection from physical damage. Otherwise, Class II (non-IS) wiring methods are required: threaded rigid or intermediate metal conduit, MI, perhaps MC-HL, and optical fiber cables, and a few flexible methods for connections requiring flexibility.

PS: Your thread title question differs from the subject matter. The direct reply to the title question "Are IS Barriers Required for Instrumentation Rated Class II?" is no.

Hello everyone!

In order to respect IS requirements please indicate the type of cables or wiring recommended to be used between barriers and EX equipment zone 1&2.

Thank you!

According to the NEC, you can use any Chapter 3 wiring method.

More correctly...

504.20 Wiring Methods. Any of the wiring methods suitable
for unclassified locations, including those covered by
Chapter 7 and Chapter 8, shall be permitted for installing
intrinsically safe apparatus. Sealing shall be as provided in
504.70, and separation shall be as provided in 504.30.

By Peter Macalua on 31 July, 2016 - 11:22 pm

The thickness standard should in the ISA handbook.